On March 9, the Office of Pipeline Safety (OPS) published an advisory to gas distribution pipeline system operators. Operators should examine the location of shut-off valves controlling gas service to permanently moored vessels (PMV) and ensure that gas service can be quickly shut down, if necessary, even during high-water conditions. If not, the valves should be moved to a location above the reasonably anticipated high-water mark or equipped to be readily accessible during high-water events. In addition, operators should review their operations and maintenance manual and their emergency response manual to ensure that procedures are in place to successfully shut down the flow of gas to PMVs when necessary, including during high-water conditions.

This advisory is a result of NTSB's investigation of a natural gas leak on a permanently moored vessel (PMV), the President Casino on the Admiral (Admiral), on April 4, 1998. The Admiral was struck by barges that detached from a tow during high-water conditions on the Mississippi River in downtown St. Louis, Missouri. The Admiral lost most of its mooring lines, causing the barge to rotate away from the quay, severing the gas service line. The natural gas did not ignite, but an emergency repair crew was unable to shut off the gas supply because the flooded regulator pit made it impossible to reach the shut-off valve. After three hours the crew was able to clamp-off the line and stop the flow of gas.

There are hundreds of PMVs in U.S. waters. This incident highlights the need to evaluate the accessibility and operability of gas service line valves serving PMVs. Although not all these valves are subject to potential high-water conditions, gas distribution pipeline system operators serving PMVs should ensure that they can promptly shut down the flow of natural gas to PMVs, even during high-water conditions.

Editor's Note: This same advice applies to any vessel that has shoreside connections to natural gas pipelines, whether permanently moored or not. It also applies to companies that install and operate these pipelines, even if they are not regulated Local Distribution Companies.